1. Field of the Invention
The present invention relates to a handle assembly for an X-ray examination apparatus, and in particular to such a handle assembly for permitting a technician to adjust the three-dimensional position of the apparatus with the aid of a support motor.
2. Description of the Prior Art
Many types of X-ray examination installations have apparatus components, such as spot film devices, which must be adjusted precisely with respect to a patient to be examined but which are too heavy to be adjusted soley by hand, thus requiring the aid of a support motor to effect such adjustment. Conventional support motors utilize for this purpose generally have a slip friction clutch, the output torque of which is carefully adjusted so as to be just below that torque necessary to adjust the apparatus against the force of gravity. The torque of the slip friction clutch is utilized in combination with the force supplied by a technician by hand to overcome gravitational and inertial forces opposing movement of the apparatus. Such support motors are customarily connected through a suitable hand switch housed in the handle assembly. The sudden connection of the torque of the support motor to the apparatus, after overcoming the restoring force of the manual switch, causes an undesired jerky starting motion of the apparatus component, particularly in the case of X-ray examination installations.
A handle assembly is disclosed in German OS No. 2739934 for displacing an apparatus component with the aid of a support motor wherein the grip portion of the handle assembly is in the form of a sleeve which is displaceably mounted in the longitudinal direction on the handle assembly. The ends of the sleeve respectively abut discs comprised of pressure-sensitive resistance material. The resistance material is interconnected in a branch of a bridge circuit associated with the control circuitry for the support motor. This handle assembly permits the apparatus component to be displaced in a relatively jerk-free manner. Additionally, substantially no switching play is felt on the handle assembly. This assembly has the disadvantage, however, of permitting control of the component in only one positioning or adjusting dimension. Moreover, construction of such a handle assembly is relatively costly and, because of the close tolerances which must be observed for the individual components, is not simple to properly adjust.